GPU usage is similar to CPU usage. It measures how much you're using your GPU. Games use the GPU differently, so usage is almost never constant. It would require more GPU power to create a scene with a lot going on compared to just staring at a wall, for example; this is even more noticeable with usage if you have V-sync or a framerate limiter on (or the game has it on) and your GPU can render far more frames than it has to. If your GPU doesn't have to do as much work to render something, its usage will go down. All of this depends on the game as well, since some are also more limited by your CPU.

LordSeifer is probably correct. It's most likely cancer. But when the scans come back, they may be negative. If that's the case, then unless you notice performance being really bad around those spikes, it's probably just the card doing what it's supposed to do.---http://pcpartpicker.com/b/GCJhttp://youtu.be/AEKc-vNv_rU - updated 11/21/2013